When performing an operation using a robot, there can be an error between a position (or a defined coordinate system) of a workpiece instructed in advance as an operation program and an actual position (or a defined coordinate system) of the workpiece. Therefore, it is necessary to perform a process of locating a position of the workpiece before starting an operation, and when there is an error, correcting the error. Noncontact sensing means, such as a laser or an image, is generally used as position detecting means for detecting the position of the workpiece. However, because procedures of receiving and processing a reflected light from an object is taken in the noncontact sensing method, there is a common technical problem that accurate position detection may not be possible depending on surface material of the object or lighting condition.
To solve such a technical problem, contact sensing methods have been proposed, as disclosed in Japanese Patent No. 2709001, Japanese Laid-open Patent Publication No. 04-340605, Japanese Laid-open Patent Publication No. 60-161085, Japanese Laid-open Patent Publication No. 60-238290, and Japanese Patent No. 2793695. In a contact position detecting method of a robot employing the contact sensing method, procedures of monitoring a contact force exerted on the robot and calculating the contact position from a position of the robot at a contact time are taken.
However, in the contact position detecting method employing the conventional contact sensing method, because a contact portion of a robot that makes contact with the workpiece is a rigid body, it is necessary to suppress the operation speed at the time of contact. Therefore, as the number of contact points of the robot with the workpiece increases, the detection of the contact point is delayed, and the operation efficiency is degraded.